1. Field of the Invention
The present invention relates to the field of airplane parts packaging. More particularly, the present invention relates to the field of turbine blade packaging containers.
2. Description of the Related Art
Airlines carry millions of spare components for unforeseen needs, emergencies, and regular maintenance. Among these spare components are fan blades for the first stage, which represents the first row of blades on modern jet engines. Events such as bird strikes, ice chunks entering the engines during flight, or gravel kicked up from the ground by a landing gear and sucked into an engine can seriously damage a turbine blade, making it necessary to replace the blade. First stage blades are the most prone to such damage. These blades can often be replaced at the line station (terminal). Airlines therefore routinely keep one or two pairs of spare turbine blades at the line stations.
Jet engine fans spin at tremendous speeds, making it imperative that the fan blades be precisely balanced to prevent vibrations. To keep the turbine fans precisely balanced, turbine blades for many jet engines are replaced in pairs. If one blade becomes unserviceable, the damaged blade and the blade opposite it are replaced together. The old blades are replaced with a new pair, with each new blade pair comprising two blades that are matched usually at the factory to have identical weights to within a few grams. To keep the blades properly matched, blade pairs are shipped and stored as pairs. Blade pairs must not only be matched for weight, they must also be matched for dynamic balance. Although a small dent or bend will not change the weight of the blade, it can change the rotational dynamic balance of the blade. Turbine blades must therefore be protected against injuries that otherwise might occur during shipping, storing, and handling. Protecting blades against damage is especially critical in light of the high cost of replacing the blades which are usually made from titanium, the extremely high cost to an airline for every hour that an aircraft is unexpectedly grounded, and the disastrous consequences that could result from installation of an unbalanced fan blade pair.
It is noted in passing that many turbine engines have an even number of blades, and the foregoing statements relating to replacing an opposing pair of blades relates mainly to such engines. However, certain turbine engines have an odd number of blades, and accurately balanced replacement blades for such engines are also important.
Turbine fan blades are irregularly shaped, as can be seen from the illustration of a typical fan blade in FIG. 1. Different fan blade models corresponding to different jet engine models also differ significantly one from another. Fan blades differ in root shapes, platform lengths and widths, blade lengths and widths, chord angles, and midspan sizes and locations. These factors have complicated the development of a suitable packaging container for fan blades.
Packaging containers having foam with recesses that follow the contours of the objects to be shipped are well known within the packaging arts. However, such contoured foam would be expensive to produce in light of the highly irregularly shaped molds that would be required for fan blades. Furthermore, shipping crates lined with foam contoured to one blade model would be unsuitable for shipping a different blade model. While removable foam components could be used, these present the additional risk that such foam components will be lost or misplaced during maintenance operations. Packing "shells" or "peanuts" and the like could be used in the container, but the heavy turbine blades can settle to the bottom of a container filled with such material increasing the possibility that the blade will be damaged during handling. Additionally, packing shells are environmentally wasteful and have a tendency to blow away in even slight breezes and create unsightly conditions. Nestling the blades within various other cushioning substances such as foam blocks or newspaper suffers the drawback of being time consuming to properly and securely pack the fan blade, with the attendant risk that the blades will not always be properly packed.